1921] e CHAMBERLAIN—GROWTH RINGS 207 
slightly thickened, but thoroughly suberized. Beneath the second- 
ary cortex is the primary, consisting of loose rounded cells with 
Fics. 3~5.—F1c. 3, Aloe ferox: normal bundle of primary polystelic region; X 100; 
fig. 4. Aloe ferox: bundle of primary polystelic region, showing clogged lumen of 
tracheids; {some of cells immediately surrounding bundle becoming meristematic; 
100; fig. 5, Aloe ferox: more advanced condition than in fig. 4; Xz1o00. 
